Multi-drug resistant bacteria refer to microorganisms that have developed resistance to multiple antimicrobial drugs. This resistance is of particular concern in the context of treating infections, as it reduces the effectiveness of available therapies. Resistance to antimicrobial drugs can be caused by various factors, including the misuse of antibiotics, improper use of drugs, as well as the mutual spread of resistance genes. Such resistance represents a challenge in the treatment of infections in the hematology department. Infection prevention also plays a pivotal role in combating antimicrobial resistance, including improving hygiene measures, infection control, responsible use of antibiotics and education of healthcare workers. Timely and appropriate antimicrobial therapy is essential in the treatment of infections caused by MDR microorganisms. The main sources of concern are Staphylococcus aureus (especially MRSA), vancomycin-resistant S. aureus, MDR Pseudomonas aeruginosa, carbapenem-resistant Acinetobacter baumannii, Escherichia coli and Klebsiella pneumoniae, vancomycin-resistant enterococci (VRE) and (XDR) Mycobacterium tuberculosis. A retrospective study was conducted on the frequency of multiresistant bacteria at the hematology department at the Zagreb Clinical Hospital Center, which indicates a high prevalence of multiresistant isolates among patients, which is expected in comparison with other European and global results. In the period from January 1 2020 until December 31 2020, a total of 560 patients from a total of 1012 hospitalizations were analyzed, of which an isolate was recorded in 100 cases, which makes the prevalence of the isolate approximately 17.86%. The most common bacteria is VRE with a share of 31%. These results suggest a significant problem with multidrug-resistant strains and lead to thinking about new prevention strategies for this group of patients. Also, further research is needed to better understand the spread and resistance mechanisms of microorganisms, as well as to develop new antibiotics and treatment strategies.